The length operator is denoted by the unary operator #.
The length of a string is its number of bytes
(that is, the usual meaning of string length when each
character is one byte).
The length of a table t is defined to be any
integer index n
such that t[n] is not nil and t[n+1] is nil;
moreover, if t is nil, n can be zero.
For a regular array, with non-nil values from 1 to a given n,
its length is exactly that n,
the index of its last value.
If the array has "holes"
(that is, nil values between other non-nil values),
then #t can be any of the indices that
directly precedes a nil value
(that is, it may consider any such nil value as the end of